[PATCH net] can: kvaser_usb: validate command format before parsing in hydra receive path

["Cen Zhang (Microsoft)" <blbllhy@gmail.com>]

The receive-path command parsers (kvaser_usb_hydra_wait_cmd and
kvaser_usb_hydra_read_bulk_callback) call kvaser_usb_hydra_cmd_size()
without verifying that enough buffer remains.  For CMD_EXTENDED,
kvaser_usb_hydra_cmd_size() unconditionally reads a 2-byte len field
at offset 4 (kvaser_usb_hydra.c:532).  A malicious USB device can place
a CMD_EXTENDED header at the end of a 3072-byte bulk transfer such that
only 4 bytes remain, causing a 2-byte slab-out-of-bounds read.

  BUG: KASAN: slab-out-of-bounds in kvaser_usb_hydra_wait_cmd+0x3f1/0x480
    [kvaser_usb_hydra.c:678]
  Read of size 2 at addr ffff888013f7ec00 by task kworker/0:0/9
   kvaser_usb_hydra_wait_cmd+0x3f1/0x480
   kvaser_usb_hydra_get_software_details+0x1c7/0x5d0
   kvaser_usb_probe+0x36a/0x1240

Additionally, if the device sends CMD_EXTENDED with len=0,
kvaser_usb_hydra_cmd_size() returns 0 and the parser loops forever
(pos += 0), permanently burning one CPU core.

Fix by adding kvaser_usb_hydra_cmd_size_rx(), a receive-path wrapper that
validates buffer bounds before calling kvaser_usb_hydra_cmd_size().
Callers check for zero return to reject both issues above.

Fixes: aec5fb2268b7 ("can: kvaser_usb: Add support for Kvaser USB hydra family")
Reported-by: AutonomousCodeSecurity@microsoft.com
Reported-by: Xiang Mei (Microsoft) <xmei5@asu.edu>
Reported-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
---
The zero-length command loop is also addressed by:
https://lore.kernel.org/linux-can/20260815-can-esd-hydra-fixes-v1-2-de644cbeaec2@ikuyo.dev/

This patch additionally handles truncated command headers in the
synchronous wait and asynchronous receive paths, including the
leftover-buffer path.

 .../net/can/usb/kvaser_usb/kvaser_usb_hydra.c | 34 ++++++++++++++++---
 1 file changed, 30 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c b/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
index efbb7bed34c9..a964edde5783 100644
--- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
+++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
@@ -536,6 +536,20 @@ static size_t kvaser_usb_hydra_cmd_size(struct kvaser_cmd *cmd)
 	return ret;
 }
 
+/* Receive-path wrapper: validate buffer bounds before reading cmd_size. */
+static size_t kvaser_usb_hydra_cmd_size_rx(struct kvaser_cmd *cmd,
+					   size_t remaining)
+{
+	if (remaining < sizeof(struct kvaser_cmd_header))
+		return 0;
+
+	if (cmd->header.cmd_no == CMD_EXTENDED &&
+	    remaining < offsetof(struct kvaser_cmd_ext, cmd_no_ext))
+		return 0;
+
+	return kvaser_usb_hydra_cmd_size(cmd);
+}
+
 static struct kvaser_usb_net_priv *
 kvaser_usb_hydra_net_priv_from_cmd(const struct kvaser_usb *dev,
 				   const struct kvaser_cmd *cmd)
@@ -675,8 +689,9 @@ static int kvaser_usb_hydra_wait_cmd(const struct kvaser_usb *dev, u8 cmd_no,
 			size_t cmd_len;
 
 			tmp_cmd = buf + pos;
-			cmd_len = kvaser_usb_hydra_cmd_size(tmp_cmd);
-			if (pos + cmd_len > actual_len) {
+			cmd_len = kvaser_usb_hydra_cmd_size_rx(tmp_cmd,
+							       actual_len - pos);
+			if (!cmd_len || pos + cmd_len > actual_len) {
 				dev_err_ratelimited(&dev->intf->dev,
 						    "Format error\n");
 				break;
@@ -2124,7 +2139,14 @@ static void kvaser_usb_hydra_read_bulk_callback(struct kvaser_usb *dev,
 
 		cmd = (struct kvaser_cmd *)card_data->usb_rx_leftover;
 
-		cmd_len = kvaser_usb_hydra_cmd_size(cmd);
+		cmd_len = kvaser_usb_hydra_cmd_size_rx(cmd,
+						       KVASER_USB_HYDRA_MAX_CMD_LEN);
+
+		if (!cmd_len) {
+			dev_err(&dev->intf->dev, "Format error\n");
+			spin_unlock_irqrestore(usb_rx_leftover_lock, irq_flags);
+			return;
+		}
 
 		remaining_bytes = min_t(unsigned int, len,
 					cmd_len - usb_rx_leftover_len);
@@ -2154,7 +2176,11 @@ static void kvaser_usb_hydra_read_bulk_callback(struct kvaser_usb *dev,
 	while (pos < len) {
 		cmd = buf + pos;
 
-		cmd_len = kvaser_usb_hydra_cmd_size(cmd);
+		cmd_len = kvaser_usb_hydra_cmd_size_rx(cmd, len - pos);
+		if (!cmd_len) {
+			dev_err(&dev->intf->dev, "Format error\n");
+			return;
+		}
 
 		if (pos + cmd_len > len) {
 			/* We got first part of a command */
-- 
2.52.0